Two of the most frequently returned response codes, 2046 and 2038 indicate that the customer’s bank is unwilling to accept the transaction - they are returned when payment authorization has been declined at the issuing bank. The causes for either are diverse and difficult to pin down without contacting the bank, but typical ones include a high level of recent activity on the card, an incorrect card number or expiration date entered on the checkout page, insufficient funds in the associated bank account, the card being over its limit and a rejection based on fraud filters at the bank. Being a soft decline (the result of a temporary issue), the best way to troubleshoot this error is to simply retry the card at a later time.
Another way to tackle this error is to enable card address fields on your chargebee web interface. This reduces 2046/2038 declines in that it makes information that is required at the issuing bank mandatory at checkout. Navigate to Settings >> Customer-facing essentials >> Checkout & Self-serve portal >> Field Configurations >> Card information and mark address lines and CVV as mandatory.
If the error persists, consider contacting the customer with a request to try a different payment method and/or send a query to her bank.